1) Field of the Invention
The invention relates to a plate-shared cutter insert, hereinafter also referred to as drill plate, for direct clamping attachment in a rotary driven base body forming on one of its end faces a centering groove that is open towards the top, wherein the centering groove is bounded by at least two opposing mounting jaws, with at least one centering face which is located in the region of the mounting jaws for providing a centering contact with the drill plate with the clamping attachment provided by a mounting screw which centers the drill plate in the centering groove.
2) Description of the Related Art
The drill plate with a clamping attachment in a base body has been disclosed, for example, in DE 197 36 598 69 C2. The upper end face of the base body hereby forms a groove that is open towards the top and in which the drill plate can be inserted. A clamping slot through which an associated clamping screw extends is arranged in the bottom of the groove.
According to the embodiment disclosed in DE 197 36 598 C2, the drill plate has diametrically opposing adjustable stop faces formed by threaded screws which are located in corresponding clamping jaws in the base body and shaped to be adjustable therein. The bolt side of the screws is supported on diametrically opposing stop faces on the drill plate.
When the drill plate is inserted into the base body, the drill plate is therefore slightly rotated about a rotation angle against the operating direction of the drill, so that the contact faces in the clamping jaws (formed by the bolt-side ends of the adjustment screws) and the associated contact faces in the drill plate contact each other for transmitting the load.
The connection is secured and formfittingly maintained by tightening a clamping screw that extends through the clamping slot.
This known arrangement has the disadvantage that the adjustment step for centering the drill plate in the base body is quite complex due to the diametrically opposing adjustment elements. Each adjustment screw has to be separately adjusted with a corresponding adjustment tool, so that the drill plate can be preliminarily centered in the base body.
Using these adjustment screws is not only complex, but disadvantageously, the clamping screw also has to be manipulated so as to finally secure the drill plate in the base body.
Accordingly, three separate elements have to be adjusted, which makes the adjustment so complex.
Disadvantageously, the adjustment elements formed by the two diametrically opposing adjustment screws are located in a different plane from the clamping screw that extends through the clamping slot.
Transfer of the clamping force to the drill plate is therefore inadequate, because the receiving opening for the drill plate has an approximately trapezoidal cross-section. As a result, due to the trapezoidal shape, the drill plate is only tightened in the upper region of the receiving groove, even if the clamping screw is tightened by applying a large torque.
As another disadvantage, the location of the clamping screw and the location of the clamping slot must be arranged relative far away below the clamping contact (receiving groove) between drill plate and base body, because (in the plane above) the adjustment elements formed as threaded screws have to be arranged.
Since the elements are mounted in separate planes, a relatively large installation space is needed, which degrades the clamping action of the drill plate in the base body.
Adjusting the adjustment elements may also present a problem, because the adjustment elements may be moved unintentionally (or even intentionally), which can misaligned the center position of the drill plate in the base body. A readjustment can then become quite complex.
In addition, this is a statically overdetermined system, because when the adjustment screws are strongly tightened for the preliminary attachment of the drill plate, the associated clamping jaws in the base body are already spread apart and therefore have to be moved towards each other and pressed against each other by tightening the clamping screw.
A transfer of high operating torques to the base body may also have the following disadvantage:
The corresponding clamping forces exerted on the drill plate are transmitted to the clamping jaws in the base body. The clamping jaws are therefore subjected to shear forces.
Because the clamping jaws are weakened by the clamping slot that extends downwardly from the groove bottom, the clamping jaws can inadvertently shear off for higher loads.
Disadvantageously, the trapezoidal centering groove receiving the drill plate is spread apart when high operating torques are transmitted, which causes high stress in the material of the clamping jaws in the base body. In addition, the drill plate is also subjected to shear forces, because it does no longer form fittingly contact the sidewalls of the deformed grooves, which may cause the drill plate to break apart.
It is therefore an object of the invention to modify a drill plate with a base body, so that the drill plate can be centered in the base body without additional adjustable stop elements, and so that greater operating torques can be transmitted to the drill plate without risking damage to the clamping jaws of the base body or to the drill plate.